1. Field of the Invention
The present invention relates to an electrophoretic display device, and more particularly, to an electrophoretic display device and a method of fabricating the same.
2. Discussion of the Related Art
In general, liquid crystal display (LCD) devices, plasma display panels (PDPs) and organic electro-luminescence displays (OELDs) have been widely used for display devices. However, recently, to meet rapidly diversified consumers' requirements, various display devices has been introduced.
Particularly, properties of a light weight, thin profile, high efficiency and function for displaying full color moving images have been required in the display devices. To satisfy the properties, electrophoretic display devices, which have merits of papers and other display devices, have been suggested and researched. The electrophoretic display devices use a phenomenon that charged particles move to an anode or a cathode. The electrophoretic display devices have advantages in a contrast ratio, a response time, a full color display, costs, portability, and so on. Differently from the LCD devices, the electrophoretic display devices do not require a polarizer, a backlight unit, a liquid crystal layer, and so on. Accordingly, the electrophoretic display devices have an advantage in production costs.
FIG. 1 is a schematic view of a related art electrophoretic display device to explain a driving principle of the same. In FIG. 1, the related art electrophoretic display device 1 includes a first substrate 11, a second substrate 36 and an ink layer 57 interposed therebetween. The ink layer 57 includes capsules 63, and each capsule 63 has a plurality of white-dyed particles 59 and a plurality of black-dyed particles 61 therein. The white-dyed particles 59 and the black-dyed particles 61 are negatively and positively charged by a condensation polymerization reaction, respectively.
A plurality of pixel electrodes 28, which are connected to a plurality of thin film transistors (not shown), are formed on the first substrate 11, and each pixel electrode 28 is disposed in each pixel region (not shown). A positive voltage or a negative voltage is selectively applied to each of the pixel electrodes 28. When the capsules 63 including the white-dyed particles 59 and the black-dyed particles 61 have various sizes, a filtering process is performed to select the capsules 63 having a uniform size.
When a positive or negative voltage is applied to the ink layer 57, the white-dyed particles 59 and the black-dyed particles 61 in the capsules 63 move towards opposite polarities according to polarities of the applied voltage. Therefore, when the black-dyed particles 61 move upward, a black color is displayed. Alternatively, when the white-dyed particles 59 move upward, a white color is displayed.
FIG. 2 is a cross-sectional view of schematically illustrating an electrophoretic display device according to the related art. In FIG. 2, the related art electrophoretic display device 1 includes a first substrate 11, a second substrate 36 and an ink layer 57 interposed therebetween. The ink layer 57 includes fifth and sixth adhesive layers 51 and 53, a common electrode 55 and capsules 63. The common electrode 55 and the capsules 63 are disposed between the fifth and sixth adhesive layers 51 and 53. The fifth and sixth adhesive layers 51 and 53 face each other and include a transparent material. The common electrode 55 is formed of a transparent conductive material. Each capsule 63 has a plurality of white-dyed particles 59 and a plurality black-dyed particles 61 therein. The white- and black-dyed particles 59 and 61 are negatively and positively charged by a condensation polymerization reaction, respectively.
The second substrate 36 includes a transparent material such as plastic or glass. The first substrate 11 includes an opaque material such as stainless steel. As occasion demands, the first substrate 11 may be formed of a transparent material such as plastic or glass. A color filter layer 40 is formed on an inner surface of the second substrate 36. The color filter layer 40 includes red, green and blue color filter patterns.
Gate lines (not shown) and data lines (not shown) are formed on the first substrate 11 in a matrix shape. The gate lines and the data lines cross each other to define pixel regions P. A thin film transistor Tr is formed at each crossing portion of the gate lines and the data lines in each pixel region P. The thin film transistor Tr includes a gate electrode 14, a gate insulating layer 16, a semiconductor layer 18, a source electrode 20 and a drain electrode 22. The gate electrode 14 extends from the gate line (not shown). The gate insulating layer 16 covers the gate electrode 14. The semiconductor layer 18 overlaps the gate electrode 14 and includes an active layer 18a and ohmic contact layers 18b. The source electrode 20 contacts the semiconductor layer 18 and extends from the data line (not shown). The drain electrode 22 is spaced apart from the source electrode 20.
A passivation layer 26 is formed on a substantially entire surface of the first substrate 11 including the thin film transistor Tr. The passivation layer 26 includes a drain contact hole 27 exposing the drain electrode 22.
A pixel electrode 28 is formed on the passivation layer 26 in each pixel region P. The pixel electrode 28 is connected to the drain electrode 22 through the drain contact hole 27. The pixel electrode 28 is formed of a transparent conductive material, for example, one of indium-tin-oxide (ITO) and indium-zinc-oxide (IZO).
The electrophoretic display device 1 having the above-mentioned structure uses ambient light, for example, natural light or room electric light, as a light source. The electrophoretic display device 1 displays images by inducing a position change of the white-dyed particles 59 and the black-dyed particles 61 in the capsules 63 depending on a polarity of a voltage selectively applied to the pixel electrode 28.
Hereinafter, a method of manufacturing the related art electrophoretic display device will be described with reference to accompanying drawings.
FIGS. 3A to 3E are cross-sectional views of illustrating an electrophoretic display device in steps of a fabricating process for the same according to the related art. For convenience of explanation, defined are a display area including a plurality of pixel regions P and a non-display area at a periphery of the display area.
In FIG. 3A, first and second adhesive layers 7 and 9 are formed on upper and lower surfaces of a first carrier substrate 5, for example, a glass substrate, respectively. First and second metal thin film substrates 11 and 13 of a stainless steel are attached to outer surfaces of the first and second adhesive layers 7 and 9, respectively.
Next, an insulating layer (not shown) is formed on substantially an entire surface of the first metal thin film substrate 11. Gate lines (not shown) and data lines (not shown) crossing each other to define pixel regions P are formed on the insulating layer. A thin film transistor Tr connected to the gate and data lines is formed in each pixel region P. Although not shown in the figure, a gate pad electrode connected to the gate line and a data pad electrode connected to the data line are formed in the non-display area at the periphery of the display area.
A passivation layer 26 is formed entirely over the thin film transistor Tr by applying an organic insulating material. The passivation layer 26 is patterned to thereby form a drain contact hole 27 exposing a drain electrode (not shown) of the thin film transistor Tr in the pixel region P, a gate pad contact hole (not shown) exposing the gate pad electrode, and a data pad contact hole (not shown) exposing the data pad electrode.
A transparent conductive material layer is formed and patterned to thereby form a pixel electrode 28 contacting the drain electrode of the thin film transistor Tr through the drain contact hole 27 in the pixel region P, a gate auxiliary pad electrode (not shown) contacting the gate pad electrode through the gate pad contact hole in the non-display area, and a data auxiliary pad electrode (not shown) contacting the data pad electrode through the data pad contact hole in the non-display area. Accordingly, an array substrate 22 for the electrophoretic display device including the above-mentioned elements may be completed.
Next, in FIG. 3B, third and fourth adhesive layers 32 and 34 are formed on upper and lower surfaces of a second carrier substrate 30, for example, a glass substrate, respectively. First and second transparent substrates 36 and 38 are attached to outer surfaces of the third and fourth adhesive layers 32 and 34, respectively. The first and second transparent substrates 36 and 38 may be flexible plastic.
A color filter layer 40 including red (R), green (G) and blue (B) color filter patterns 40a, 40b and 40c sequentially arranged is formed on the first transparent substrate 36. Each of the red (R), green (G) and blue (B) color filter patterns 40a, 40b and 40c corresponds to the pixel region P in the array substrate 22. Accordingly, a color filter substrate 42 for the electrophoretic display device including the above-mentioned elements may be completed. Here, a black matrix (not shown) may be further formed. The black matrix overlaps edges of the color filter patterns 40a, 40b and 40c and surrounds each pixel region P.
In FIG. 3C, an electrophoresis film 65 is attached to the array substrate 22. The electrophoresis film 65 includes fifth and sixth adhesive layers 51 and 53, a common electrode 55 and an ink layer 57. The ink layer 57 is disposed between the fifth and sixth adhesive layers 51 and 53. The common electrode 55 is formed of a transparent conductive material and is disposed between the sixth adhesive layer 53 and the ink layer 57. The ink layer 57 includes a plurality of capsules 63, and each capsule 63 has a plurality of white-dyed particles 59 and a plurality black-dyed particles 61 therein. The white-dyed and black-dyed particles 59 and 61 are negatively and positively charged by a condensation polymerization reaction, respectively. The fifth adhesive layer 51 faces the pixel electrode 28 such that the ink layer 57 is positioned between the common electrode 55 and the pixel electrode 28.
In FIG. 3D, the color filter substrate 42 is disposed such that the color filter layer 40 faces the electrophoresis film 65 and then attached to electrophoresis film 65 bonded to the array substrate 22 to thereby form a panel.
In FIG. 3E, the first carrier substrate 5, the first and second adhesive layers 7 and 9, and the second metal thin film substrate 13 are detached from the first metal thin film substrate 11 of the array substrate 22 of FIG. 3D. Subsequently, the second carrier substrate 30, the third and fourth adhesive layers 32 and 34, and the second transparent substrate 38 are detached from the first transparent substrate 36 of the color filter substrate 65 of FIG. 3D. Accordingly, the electrophoretic display device 1 can be obtained.
However, there are disadvantages in the above-mentioned fabricating process for the related art electrophoretic display device. The array substrate requires steps of attaching the first and second adhesive layers on the upper and lower surfaces of the first carrier substrate, attaching the first and second metal thin film substrates on the first and second adhesive layers, and forming the array elements, for example, the thin film transistor or the pixel electrode, on the first metal thin film substrate attached on the first adhesive layer. Moreover, the color filter substrate requires steps of attaching the third and fourth adhesive layers on the second carrier substrate, attaching the first and second transparent substrates on the third and fourth adhesive layers, and forming the color filter layer on the first transparent substrate. In addition, unessential elements, for example, the first and second carrier substrates, are detached from the panel. Accordingly, the fabricating process is very complicated.
Furthermore, when the unessential elements, which are required in the fabricating process for the electrophoretic display device but are not required in the completed electrophoretic display device, are detached, there may be stresses, and misalignment may be caused between the array substrate and the color filter substrate. Accordingly, this causes degradation of image qualities.
In addition, there may be scratch damages on the first transparent substrate, which is formed of a relatively low hardness material such as plastic, during attaching and detaching steps.